The oil and gas industry has long sought seamless oilfield tubulars in standard sizes that can resist corrosion found in deep hot and sour wells. It would be useful and desirable to have corrosion resistant tubulars from which downhole tools and assemblies might be fabricated. Significant resources have been devoted to fabrication of such tubulars from high nickel content alloys, such as N06625, N10276 and N07716.
Any number of United States patents has been issued describing the beneficial aspects of Ni alloys in sour oil and gas applications. See for example U.S. Pat. No. 6,315,846 to Hibner et al., U.S. Pat. No. 5,217,684 to Igarashi et al., U.S. Pat. No. 4,400,210 and U.S. Pat. No. 4,400,211 to Kudo et al., U.S. Pat. No. 4,245,698 to Berkowitz et al. Other United States patents have been issued for other combinations of alloying elements including U.S. Pat. No. 6,730,264 to Cao, U.S. Pat. No. 5,556,594 to Frank et al., U.S. Pat. No. 5,310,523 to Culling, U.S. Pat. No. 5,246,661 to Culling, U.S. Pat. No. 4,985,091 to Culling, most of which sought to decrease the percentage of Ni in the combination because of the high price of this scarce raw material. Other United States patents have issued for various heat treatment processes, which seek to establish the desired physical characteristics of the material. These include U.S. Pat. No. 7,156,932 to Cao et al., U.S. Pat. No. 6,638,373 to Pike Jr. et al. and U.S. Pat. No. 3,871,928 to Smith, Jr. et al.
The corrosion resistance and physical characteristics desired for oilfield tubulars make extrusion of readily machinable tubulars difficult to accomplish. So far as known to applicant, no one has previously created a oilfield corrosion resistant seamless tubular from N06625 or N07716 nickel alloys in standard oilfield lengths; and, specifically, no one has created a waste water and drilling fluid injection screen from such alloys for use in wells to permit disposal of the produced water, or other waste products, back into the formation from which it came or to inject chemicals to pressurize the formation to aid in production or any applications where fluids or semi-solids are to be injected into or withdrawn from a down hole environment. All references will use the Uniform Numbering System method of designation of the alloy composition as prescribed by ASTM and SAE.
Although the corrosion resistant properties of nickel alloys are well known, the cost and difficulty of manufacturing seamless oilfield standard length tubulars has long been deemed insurmountable. One method of accomplishing this might be the drilling of nickel alloy bar, then cold pilgering the resultant tubular, to achieve the lengths required. While this might be possible with a portion of the teachings of this application, because of the resultant waste from the drilling process, no one would rationally try to fabricate oilfield tubulars in this manner. Applicant has overcome all of these obstacles to fashion a seamless oilfield length tubular that can be used to fabricate an injection screen for a deep hot and sour environment.
The present application contains the description of a process for making these seamless oilfield tubulars in standard lengths having both the physical characteristics of corrosion resistance and high strength required for service in deep oil and gas wells, which can be machined within high tolerances needed for modern complex down hole mechanical devices. Standard oilfield or OCTG lengths vary within narrow ranges for the two most commonly used standard oil field lengths designated the R2 which is 28-32 feet in length, and the R3 which is 38-43 feet in length. The alloy used in this method works well under both conditions and is therefore well suited to oil and gas field use. The fabrication of nickel alloys in these standard lengths has not been readily accomplished. Previous attempts to do so have resulted in tubulars so difficult to machine, most have stopped trying to do so. Having fabricated a machinable oilfield tubular out of nickel alloy as described herein, the completion of the tubular by machining can be readily accomplished.
Well screens, which have long been used to either drain or inject fluids into a well bore, are a pertinent example. The technology for the manufacture of such screens has long recognized the need to create slots, such as by cutting, which provided keystone apertures tapered in cross section. See, for example, U.S. Pat. No. 1,207,808, issued 12 Dec. 1916. Often, these keystone slots are made by cutting the surface, then compressing the exterior surface to close the slot at its exterior edge to form a lip. See also, U.S. Pat. Nos. 1,652,208, issued 13 Dec. 1927, and 2,358,873, issued 26 Sep. 1944.
Modern developments seek to improve these old methods of creating uniform spacing in the slots in smaller widths. Slots having widths between 0.015 and 0.025 inches, while for many applications preferred widths would require uniform slots of approximately 0.005 to 0.007 inches to prevent the ingress of sand particles into the tubular screen. A number of more recent patents seek to create a uniform exterior lip to each slit by a variety of techniques. See, for example, U.S. Pat. Nos. 6,112,570, issued 5 Sep. 2000; 6,898,957, issued 31 May 2005; 7,069,657, issued 4 Jul. 2006; 7,073,366, issued 11 Jul. 2006.
The techniques for making well screens with these high nickel alloy have not been successful because of the work hardening properties of these nickel alloys which makes the finished product less capable of standing up to the rigors of the deep well applications. Improper machining can lead to early stress fractures and catastrophic failures in these types of wells. Accordingly, applicant has developed a fabrication process that permits the tools, such as these screens, to be fashioned with the finished product having the physical characteristics to withstand the harsh well environment in which they are intended to be placed.